<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .parents {
            width: 700px;
            height: 700px;
            display: grid;
            grid-template: repeat(3,200px)/repeat(3,200px);
            background-color: rgb(244,244,244);
            justify-content: center;
            align-content: center;
            align-items: center;
            justify-items: center;
        }

        .child {
            width: 150px;
            height: 150px;
            background: linear-gradient(135deg, #328af0, #09b2d6);
            color: white;
            border-radius: 10px;
            text-align: center;
            line-height: 150px;
        }
    </style>

</head>

<body>
    <div class="parents">
        <div class="child">1</div>
        <div class="child">2</div>
        <div class="child">3</div>
        <div class="child">4</div>
        <div class="child">5</div>
        <div class="child">6</div>
        <div class="child">7</div>
        <div class="child">8</div>
        <div class="child">9</div>
    </div>
</body>

</html>